What is HCM and why does it matter?
Hypertrophic cardiomyopathy (HCM) is a heart condition in which the walls of the heart's left ventricle thicken over time. It's the most common heart disease in cats, and Maine Coons are among the breeds with an identified genetic predisposition.
Severity varies widely from cat to cat. Some cats with HCM live full, symptom-free lives and the condition is only ever noted on a cardiac exam, while others may eventually develop signs such as lethargy, reduced activity, labored or rapid breathing, or in more serious cases, sudden collapse. Because early HCM often produces no outward symptoms at all, it usually can't be diagnosed by watching a cat's behavior at home — it typically requires an echocardiogram (a cardiac ultrasound), generally performed or reviewed by a veterinary cardiologist, to see the heart wall thickness directly.
A specific genetic mutation associated with HCM has been identified in Maine Coons, and a DNA test can check for it. However, that test doesn't tell the whole story: some cats that test negative for the known mutation still go on to develop HCM, and researchers believe other genetic and possibly environmental factors are also involved. This is a key reason why responsible breeding programs rely on periodic cardiac ultrasound screening of breeding cats throughout their breeding lives, rather than treating a single DNA test or a single clear echocardiogram as a permanent guarantee — HCM can develop or progress later in life, so cats are typically rescreened every year or two.
None of this is a substitute for veterinary guidance on an individual cat. If you notice changes in your cat's breathing, energy level, or appetite, or simply want a baseline sense of heart health, a licensed veterinarian (and a veterinary cardiologist for a full echocardiogram) is the right resource. If you have questions about the cardiac screening behind a specific litter, feel free to contact us — you can also see current available kittens.